Magnetic control means for an electronic musical instrument



June 7, 1966 F. L. WALKER 3,255,293

MAGNETIC CONTROL MEANS FOR AN ELECTRONIC MUSICAL INSTRUMENT Filed Oct. 30, 1963 2 Sheets-Sheet 1 TONE sou/v0 SIGNAL PRODUC/NG DETECTOR MEANS ea K88 ,8 22 CARR/7? CARR/El? ro/vE s/a/vAL uoouLAmr? S/GIVAL GENERATOR MES-ANS GENERATOR a0 a2 a4 (/6 .56 94 'l/w [Aw TONE SIG/VAL .96 DETECTOR l saw/0 m0 PRODUCING m 3 .i il

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MAGNETIC CONTROL MEANS FOR AN ELECTRONIC MUSICAL INSTRUMENT Filed Oct. 30, 1963 2 Sheets-Sheet 2 K as gas CARR/ER K ro/v sou/v0 SIGNAL SIG/VAL -P/?00uc//va G/VRA7Z9R DETECTOR MEANS r Iil T-fl U 70 as F /4 a f7 F/G. 5a 0 H6174 F/G. 76

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FRANC/S LEE mu KER //0 BY J 5 ATTORNEY United States Patent 3,255,293 MAGNETIC CONTROL MEANS FOR AN ELEC- TRONIC MUSICAL INSTRUMENT Francis Lee Walker, 526 Charles Ava, Barrington, NJ. Filed Oct. 30, 1963, Ser. No. 320,180

' 2 Claims. (Cl. 84-1.1)

The invention relates to magnetic control means for an electronic musical instrument, and more particularly to magnetic means for controlling the amplitude and tonal qualities of an electronic musical instrument.

The advantages of the piano over its early competitors, the harpsichord and the clavichord, was in its pianoforte touch, or the ability of the pianist to control the loudness of the notes being produced by the force with which re spective keys of the keyboard were struck. While large pipe organs have the greatest compass of all instruments, the organ is still incomplete without the pianoforte touch. A more musically complete instrument than either the piano or organ would be one that combines the compass of the organ and the control of the piano.

It is, therefore, a primary object of the invention to provide a new and improved magnetic control means for an electronic musical instrument allowing the operator to control by touch the loudness of the notes produced.

Another object of the invention is to provide a new and improved magnetic control means for an electronic musical instrument which is highly versatile in producing actuation of the keys of a keyboard.

Another object of the invention is to provide a new and improved magnetic control means for an electronic musical instrument which is highly efiicient in operation,

rugged in construction and readily maintained in operative condition.

Another object of the invention is to provide a new and improved magnetic control means for an electronic musical instrument allowing the instrument to be played and controlled in a manner similar to the piano.

The above advantages, as well as many other advantages of the invention, are achieved by providing a magnetic control means for-an electronic musical instrument with a first magnetically saturable core element having a magnetically coupled signal input lead and a magnetically coupled signal output lead. The first unit produces a space varying magneticfield, and a movable key member controlla-bly positions the unit with respect to the first core element for controlling and varying the degree of saturation of said first core element.

A second magnetically saturable core element is pro vided having a lead magnetically coupled with the second core element and connected in series with the output lead of the first core element for providing an output signal from the series connected first and second core elements. A rotatable unit driven with a constant angular velocity has a periphery positioned proximate to the second core element and provides a magnetic field varying angularly in space about its periphery.' 1

The key member has a normal position in which said first unit is positioned with its magnetic field saturating the first element so that signals at the input lead are not delivered to the output lead of the first core element. The key member, when actuated from its normal position,

moves the first unit to a more distant position with respect to the first core elment, so that the magnetic field of the first unit no longer fully saturates the first core ice element and signals at its input lead are delivered at the output lead of the first core element.

A signal generating means delivers a carrier input signal to the series connected first and second core elements and an audio detecting and sound producing means is energized by the out-put signal derived from the series con nected first and second core elements when the key member is actuated from its normal position. The sound producing means provides a sound having percussive or transient qualities and amplitude determined by the actuation of the key member, while the tonal qualities and pitch are related to the modulationof the carrier signal by the second unit.

Several other embodiments and modifications embodying the invention are disclosed hereinbelow.

The foregoing and other objects of the invention will become apparent as the following detailed description of the invention is read in conjunction with the drawings, in which:

FIGURE 1 is a sidee elevational view partially in block form of magnetic control means for an electronic musical instrument embodying the invention,

FIGURES 2, 3 and 4 are side elevational views partly in block form of respective modified forms of the means shown in FIGURE 1,

FIGURE 5 is a hysteresis curve used for disclosing the fully saturated and partially saturated regions of the magnetic core elements described in connection with FIGURES 1 through 4,

FIGURES 6a, 7a, 8a and 9a are side elevational views of respective rotatable units having various peripheral configurations producing respective magnetic fields varying angularly in space about their peripheries, while FIG- URES 6b, 7b, 8b and 9b show in graphic form the periodic modulation signal produced respectively by said magnetic rotatable units.

Like reference numerals designate like parts throughout the several views.

Referring to FIGURE 1, an electronic musical instrument it] is provided with a keyboard 12 having a bed 14 supporting a plurality of key members 16 in elongated form or key members 16' of short and raised form shown in dashed lines for producing sharp or flat notes. The keyboard 12 is of conventional construction having a screw element 18 for raising and lowering the key depressing limit pad 20. A key level adjustment screw element 22 has its end 24 threadedly engaged with the.

key member 16, while its head end 26 is movable through an opening 28 in the bed 14. The bed 14 is also provided with guide pins 30, 32 which have respective ends 34, 36 extending into openings 38, 40 in the key member 16 provided with padding means-therein. The guide pin 32 positions a fulcrum block 42 having a rounded top between the bed 14 and the key member 16. The

key member 16 is maintained in a normal level position by a key return spring 44 connected between the bed 14 and the end 46 of the key member 16.

A lever 48 having an end 50 secured by screw elements 52, 54 with the end 46 of the key member 16 is provided with a magnetic unit 56 secured at its extending end 58. A fulcrum 60 secured with the key member 16. between the screw elements 52, 54, allows the adjustment of the inclination of the lever 48 by loosening and tightening of the screw elements 52, 54.

A supporting block 62 is attached to the end of the key bed 14 mounting at its top 64 a toroidal core element 66 having magnetic properties represented graphically in FIGURE 5.

A typical hysteresis or magnetization curve is shown for the core element 66 with flux density B plotted against magnetizing force H. vWith the element 66 completely demagnetized, the initial application of a magnetizing force H produces a magnetic flux density B, as shown by the curve 67. When the magnetizing force is sufiiciently large, the curve 66 has a substantially horizontal straight line in portion 68 showing that the core element 66 is fully saturated. The application of further magnetizing force H has no aifect upon the flux density B. With the removal of the magnetizing force H, the flux density in the core element 66 is represented by the curve 71) which has an increasing slope, as the magnetizing force H is-reduced. When the magnetizing force is zero, a residual flux density remaining in the core element 66 is shown as B If a magnetizing force H is now applied to the core element 66, the flux density B produced will be represented by the curve 71) and with the increased application of the magnetizing force H, the core element 66 will return to its fully saturated condition illustrated at 680i FIGURE 5.

The core element 66 is positioned proximate to the magnetic unit 56 with the key member 16 in its normal position shown in FIGURE 1. The magnetic field provided at the core element 66 with the key member 16 in its normal position, saturates the core element 66, so that same is placed in a condition represented by the substantially horizontal portion 68 of the curve shown in FIG- URE 5. The key member 16 is actuated by moving its end 69 downwardly, so that its end 46 pivots upwardly, resulting in the movement of the magnetic unit 56 away from the core element 66. This reduces the intensity of the magnetic field at the core element 66, so that the core element is only partially saturated, represented by the curved or knee portion 70 of the curve in FIGURE 5. The intensity of the magnetic field produced at the core element 66 may be adjusted by varying the inclination of the extending lever 48, by choosing a permanent magnet to produce the desired magnetic field strength, or where an electromagnet is used for the magnetic unit 56, varying the actuating current to adjust the intensity of the magnetic field produced. By adjusting the key depression limit screw 18, the maximum reduction of the magnetic field at the core element 66 in the partially saturated region 70 of FIGURE 5, when the key member 16 is actuated, may be limited.

The core element 66, which may be made of a ferrite material or other material having suitable magnetic properties, represented by the curves in FIGURE 5, has a sig nal input lead 72 which is magnetically coupled to the core element 66 by a loop or winding 74 which is returned to ground potential, and has a signal output lead 76 which is also magnetically coupled with the core element 66 by a loop or winding 78 which is similarly returned to ground V potential.

A signal generatore80 provides a signal with constant amplitude which may, for example, have a frequency in the range of kilocycles to one megacycle. The signal from the generator 80 is delivered to a carrier modulator means 82 which also receives a signal from a tone signal generator 84. The tone signal generator provides a signal of constant amplitude having a frequency in the audible range which is to be reproduced as a musical sound.

The modulator means 82 delivers an output signal to the input lead 72 of the core element 66 comprising the carrier signal modulated by the tone or audio signal.

The signal output lead 76 is connected to the input of a tone signal detector 86 which demodulates the carrier signal and delivers the tone or audio signal to a sound producing means 88.

In the use of the electronic musical instrument 10, the operator manipulates the key members 16 of the keyboard 12 by depressing or striking selected ones of the keys 16, 16 corresponding to musical notes for producing sounds having the frequency or pitch of the selected musical notes. When a key member 16 is not depressed, the core element 66 of instrument 10 is positioned proximate to the magnetic unit 56 and has its core saturated by magnetic flux. When in this condition, the delivery of the signal to the input winding 74 of the core 66 does not change the flux density within the core 66 due to its saturated condition. Hence, the flux does not vary in the core 66 and a signal voltage is not induced in the winding 78, so that an output signal is not delivered to the output lead 76 of the core element 66. Thus, no sound is produced by the means 88 under such conditions. However, when a key member 16 or 16' is depressed or struck, the magnetic unit 56 is moved away from the core element 66 and the core element 66 is no longer fully saturated, but operates along the portion of the curve shown in FIG- URE 5. Under the circumstances, the magnetic field pro duced by the input winding 74 does have an alfect and varies the magnetic flux in the core 66, so that an output signal is induced in the winding 78 which is delivered to the output lead 76 of the core element 66. Thus, a signal is delivered to the detector 86 which delivers an audio signal to the sound producing means 88 for providing a sound with the tone or frequency of the signal delivered by the signal generator 84. It is particularly noted that the degree of saturation of the core element 66 decreases responsive to the amount that the key member 16 is depressed. Also, the slope of the curve in the region 70 increases as the degree of saturation of the core element 66 decreases with the depression of the key member 16. With the increasing slope of the portion 70 of the saturation curve, the change in flux within the core element 66 responsive to the input signal to the lead 72 correspondingly increases and induces an output signal at the output lead 76 which is correspondingly larger in amplitude. By such means, the amplitude of the sound produced by the means 83 is controlled by the extent that the key member 16 is depressed. In a like manner, the rapidity with which the key members 16 are struck or depressed and released affects the speed with which the core element 66, which acts as a signal gate, is turned on and oiT. This controls a percussive or transient quality of the sound being produced by the means 88.

The magnetic control means of the electronic instrument it? provides a keyboard having key members 16 and 16 which allow the production of musical tones at selected times having loudness and precussive or transient qualities determined and instantly controlled by the touch of the operator.

FIGURE 2 illustrates an electronic musical instrument 96 which is a modified form of the instrument 10. The description provided in connection with the instrument 10 is also applicable thereto, and the differences only, therefore, will be described in detail.

In this embodiment, the carrier signal generator delivers the carrier signal directly to the input lead 72 of the core element 66 and the carrier signal is received by the output lead 76 when the key member 16, 16' is actuated from its normal position. The output lead 76 of the core element 66 is connected to the input lead 92 of a core element 94 which may be identical to the core' element 66. The core element 94 is also provided with an output lead 96. The input and output leads 92, 96 are magnetically coupled with the core element 94 by being connected to the opposite ends of an inductance winding 98 about the core element 94. The mounting block 62' attached with the key bed 14 provides for mounting the core element 66 and supports the core element 94 proximate to a rotatable mounted magnetic unit 166. The magnetic unit 160 is driven with a constant angular ve locity by a motor 102.

The form of the periphery of the magnetic unit 100 is shown in enlarged form in FIGURE 6a. The unit 100 may be made of a permanent magnet material to provide a magnetic field about its periphery 104 which varies in space as an angular function about its central axial opening 101. Rotation of the magnetic unit 100 about an axial shaft through its opening 101 with its periphery 104 positioned proximate to the core element 94 subjects the core element 94 to a magnetic field which varies periodically with a frequency depending upon the angular ve locity of the rotating unit 100.

Referring to FIGURE 5, the magnetizing force provided to the core element 94 by the unit 100 is along the region 70, representing partial saturation of the core element 94. The degree of saturation varies periodically about a point on the region 70 of the magnetizing curve in FIGURE 5 and has the affect of varying the reactance of the winding 98 coupled with the core element 94. The

variation in reactance of the winding 98 which is connected in series between the lead 76 of the core element 66 and the input to the tone signal detector 86 has the affect of amplitude modulating the carrier signal. delivered to the tone signal detector 86. The modulation signal has a waveform which is determined by the angularly varying space field provided by the rotating element and a frequency determined by the angular velocity of the rotatable unit 100.

FIGURE 6b is a graphic illustration of the modulation waveform produced by the rotatable unit 100 shown in FIGURE 6a. Similarly, the rotatable unit 106 having a periphery with the rectangular configuration shown in FIGURE 7a provides a modulation waveform shown in FIGURE 712, while the rotatable unit 108 of FIGURE 8a provides a modulation waveform shown in FIGURE 8b, and the rotatable unit 110 of FIGURE 94: provides a modulation waveform corresponding to that shown in FIGURE 9b. To produce the modulation waveforms shown, the rotatable units 110, 106, 108 and 110 used were magnetically polarized to provide lines of magnetic force within the units having a north-south direction perpendicular to the plane of the figures and parallel to their central axes of rotation, and rotated in the counterclockwise direction.

In the operation of the instrument 90, the actuating of the key members 16, 16 control the amplitude and the rise time of'the carrier signal which is delivered by the output lead 76. However, in this case, an unmodulated carrier signal is controllably delivered through the core element 66 to the winding 98 of the core element 94. The carrier signal which passes through the winding 98 of the core element 94 to the detector 86 has its amplitude further modulated by a periodic waveform having a preetermined frequency and harmonics. This waveform is produced by the periodically varying magnetic field produced by the rotating unit 100. By providing modulation waveforms having different harmonic contents, sounds with different varied tonal qualities may readily be produced by the means 88. Thus, the versatility of the control means of electronic musical instrument 90 is evident for producing many different effects and desired qualities by varying the configurations of the rotating units or otherwise controlling the form of the periodic magnetic. force produced at the core element 94 for varying the reactance of its winding.

Referring to FIGURE 3 which discloses a magnetic control means for an instrument 112 which is a modified form of the instrument 10 being provided with a supporting block 114 connected at the end of the key bed 14 providing the rotatable unit 100' mounted with its periphery proximate to the core element 66. Otherwise, the instrument 112 is substantially similar to the instrument 10, ex

cept as explained below. In this connection, it is also noted that the unmodulated carrier signal from the generator 80 is delivered to the input lead 72 of the core element 66.

In operation, when the key member 16 is not actuated, the proximity of the magnetic unit 56 to the core element 66 fully saturates the core element 66, thereby preventing the induction of an output signal for delivery at the output lead 76 of the core element 66. Under conditions of saturation, the varying additional field provided by the rotatable unit 100 has no affect in producing an output signal at the lead 76. This is seen from the curve effective for varying the degree of saturation of the core element 66 and periodically varies the amplitude of the induced carrier signal being delivered to the output lead 76 of the core element 66, As explained in connection with the control means 90, a modulation signal will have a predetermined frequency providing the pitch of the sound and a harmonic content giving the tonal qualities for the sound produced by the means 88. The operation of the instrument 112 is similar to the operation of the modified forms of instruments 10 and -with the loudness and percussive or transient qualities of notes produced being individually and instantaneously controlled by the touch of the operator upon the key members 16 of the keyboard 12 of the electronic musical instrument 112.

Refer to FIGURE 4 which discloses a magnetic control means for an electronic musical instrument 116 which is a further modified form of the control means of the instrument 112.

The magnetic control means of the instrument 116 differs from that of the instrument 112 by providing a supporting block 118 secured with the key base 14 which supports the core element 66 above a magnetic unit 56. The block 118 also rotatably supports a unit 120 over the core element 66 with its peripheral regions 122 proximate to the core element 66'.

The unit 120 is made of a material having good magnetic flux conducting properties, such as soft iron, which readily loses its magnetism so that it does not provide a permanent magnet with a magnetic field.

The core element 66' has a signal input lead 72 and signal output lead 76 magnetically coupled with the core element 66' by respective loops or windings. In its normal position, the key member 16 supports the magnetic unit 56, which may be a permanent magnet or an electromagnet, at a distance from the core element 66', so that the core element 66' is not in the partially or fully saturated condition. Under such conditions, the carrier signal delivered to the input lead 72' of the core 66' produces a varying magnetic flux which is a function of time, inducing the carrier signal in the winding of the output lead 76 which is delivered to the tone signal detector 86.

At this time, the rotating unit 120, which rotates at a constant predetermined angular velocity, has no affect on the operating conditions of the magnetic core element 66 and, therefore, does not affect the amplitude of the carrier signal delivered to the output lead 76'. Since a modulated signal is not delivered to the detector 86, an audio output signal is not produced, so that the means 88 is not energized for producing an output sound.

When the key 16 is depressed, moving the magnetic .unit 56' closer to the core element 66', its field results in the partial saturation of the core element 66'. At this time, the rotating unit 120, which provides a good magnetic path for the flux induced by the input winding energized by the lead 72', is effective in periodically 'varying the degree of saturation of the core element 66 as it rotates, due to the variation in conductivity of the magnetic flux by the unit 120 by varying the proximity of its periphery 122 to the core element 66.

As the degree of saturation of the core element 66 is increased from its fully unsaturated condition, the effect 'of the rotating unit 120 is increased, thereby increasing the modulation of the carrier signal from the generator 80 which is delivered to the tone signal detector 86. The detector 86 delivers the modulation audio signal to the sound producing means 88 for producing a tone corresponding to the key member 16 which is actuated. As previously explained in connection with the magnetic unit 100, the waveform of the modulation signal in this case is also determined by the form of the periphery 122 of the rotatable unit 120. Thus, by varying the shape of the periphery 122, modulation signals may be produced having different harmonic content, and, therefore, giving different tonal qualities which may be desired. The frequency 0r pitch of the sound, as determined in connection with the rotatable magnetic unit 100, is a function of the angular velocity of the unit 120 and the number of repetitive forms about the circumference 122' of the unit 120.

The disclosed magnetic control means for electronic musical instruments has versatility and afi'ords control of loudness unavailable in the prior art and provides an instrument with the composite advantages ofthe piano and pipe organ by including the controls of the piano and the large variation of stops or tonal qualities available in the organ. The control of the electronic instrument by the touch of the performer allows the use of abilities already acquired in connection with the piano, while produc ing effects which have not been attainable in the musical sound produced by pipe organs.

It will, of course, be understood that the description and drawings, herein contained, are illustrative merely, and that various modifications and changes may be :made in the structure disclosed without departing from the spirit of the invention,

What is claimed is:

l. A magnetic control means for an electronic musical instrument comprising a magnetically saturable core element having an input lead and an output lead magnetically coupled therewith; a rotatable magnetically conductive unit having a periphery positioned proximate said core element for periodically varying the degree of saturation upon saturation of said core element; a magnetic field producing device; a movable key member for controllably positioning said device with respect to said core element for controlling the degree of saturation of said core element; and means for rotating said unit, said key member having a normal position in which said device is positioned so that said core element is unsaturated so that signals at the input lead are delivered to the output lead of said core element, and having an actuated position in which said device saturates said core element and said rotating unit periodically varies the degree of saturation of said core element by varying the conductance of magnetic flux therethrough as a function of time.

2. The means of claim 1 including a signal generating means for delivering a carrier signal to the input lead of said core element for delivery to the output lead of said core element, an audio detecting means deriving unmodulated carrier signals from the output lead of said core element when said key member is in its normal position and deriving carriersignals modulated by a periodic audio signal produced by said rotating unit and delivering an audio output signal when said key is actuated from its normal position, and a sound producing means receiving detected output signals of said detecting means for producing sounds having tone qualities and pitch related to the modulation of said carrier signal.

References Cited by the Examiner UNITED STATES PATENTS 1,823,716 10/1931 Young 84--1.23 2,142,580 1/1939 Williams.

2,314,496 6/1939 Hammond 84-127 X 2,669,670 2/1954 Eggers 841.01 X 2,772,594 12/1956 Rowe 84--1.11 3,133,256 5/1964 Denelsbeck et al. 332-29 X FOREIGN PATENTS 1,308,996 10/ 1962 France.

1,008,094 5/1957 Germany.

1,138,995 10/1962 Germany.

ARTHUR GAUSS, Primary Examiner.

I. C. EDELL, Assistant Examiner. 

1. A MAGNETIC CONTROL MEANS FOR AN ELECTRONIC MUSICAL INSTRUMENT COMPRISING A MAGNETICALLY SATURABLE CORE ELEMENT HAVING AN INPUT LEAD AND AN OUTPUT LEAD MAGNETICALLY COUPLED THEREWITH; A ROTATABLE MAGNETICALLY CONDUCTIVE UNIT HAVING A PERIPHERY POSITIONED PROXIMATE SAID CORE ELEMENT FOR PERIODICALLY VARYING THE DEGREE OF SATURATION UPON SATURATION OF SAID CORE ELEMENT; A MAGNETIC FIELD PRODUCING DEVICE; A MOVABLE KEY MEMBER FOR CONTROLLABLY POSITIONING SAID DEVICE WITH RESPECT TO SAID CORE ELEMENT FOR CONTROLLING THE DEGREE OF SATURATION OF SAID CORE ELEMENT; AND MEANS FOR ROTATING SAID UNIT, SAID KEY MEMBER HAVING A NORMAL POSITION IN WHICH SAID DEVICE IS POSITIONED SO THAT SAID CORE ELEMENT IS UNSATURATED SO THAT SIGNALS AT THE INPUT LEAD ARE DELIVERED TO THE OUTPUT LEAD OF SAID CORE ELEMENT, AND HAVING AN ACTUATED POSITION IN WHICH SAID DEVICE SATURATES SAID CORE ELEMENT AND SAID ROTATING UNIT PERIODICALLY VARIES THE DEGREE OF SATURATION OF SAID CORE ELEMENT BY VARYING THE CONDUCTANCE OF MAGNETIC FLUX THERETHROUGH AS A FUNCTION OF TIME. 